The technical field of this disclosure is high frequency ballast systems, particularly, a high frequency electronic ballast with rail voltage switching.
High Intensity Discharge (HID) lamps, such as mercury vapor, metal halide, high-pressure sodium, and low-pressure sodium, are used for a variety of lighting tasks. As HID lamps have become more popular, electronic ballasts for HID lamps have been developed.
One challenge with electronic ballasts for HID lamps is to improve efficiency. Typically, electronic ballasts receive power from a mains power supply at one mains voltage, which is converted to another DC rail voltage, which is modulated to power the HID lamp. Although the individual electronic ballast is usually designed to operate over a range of mains voltage, the DC rail voltage is held to a set value regardless of the mains voltage. The greater the difference between the mains voltage and the DC rail voltage, the greater the power losses and the lower the efficiency.
It would be desirable to have an electronic ballast with rail voltage switching that would overcome the above disadvantages.